(a) Technical Field
Embodiments of the present invention relate generally to flexible circuit fabrication. More specifically, embodiments of the present invention relate to a roll-to-roll exposure system for manufacturing a flexible circuit film.
(b) Description of the Related Art
A roll-to-roll digital exposure system has been disclosed in, for example, U.S. Pat. No. 8,486,593, which is incorporated by reference herein. A roll-to-roll digital exposure system patterns a flexible film carried on rolls or a non-elastic belt or a conveyer, using an image measuring device and an exposing device.
In roll-to-roll systems, an error in overlay may be caused by distortion of the flexible film due to strain bias, absorption of water or solvents, tension in the flexible film, thermal history, and the like. A roll-to-roll digital exposure system minimizes this overlay error by sensing distortion of a flexible film due to those factors and controlling a spot beam from an exposing device accordingly. That is, an image measuring device reads the positions of a plurality of marks on a previous layer of the flexible film, and a computer system determines the amount of distortion of the flexible film by comparing the positions of the marks read by the image measuring device with the positions of reference marks. Then, an exposure unit patterns a subsequent layer by applying an algorithm that corrects for distortion on the basis of the degree of determined distortion.
A roll-to-roll digital exposure system thus uses the positions of an exposure unit and an ASU (Alignment Scope Unit) in a roll-to-roll system in order to minimize overlay in patterning.
In practice, there is a need for an overlay function to manufacture a device with a layered structure (layered circuit film), in which there is a need for a reference mark array for measuring the position of an alignment scope unit and the position and orientation of an object.
Further, optomechanical drift is generated in an off-axis alignment system. The optomechanical drift adds inaccuracy to this overlay function because a base line corresponding to the distance between an alignment scope unit and an exposure position (the position of a beam spot of an exposure unit) is changed. The position of an alignment scope unit should remain more precisely defined to periodically measure drift components.
The above information disclosed in this Background section is only for enhancement of understanding of the background of the invention and therefore it may contain information that does not form the prior art that is already known in this country to a person of ordinary skill in the art.